Organophosphorus Pesticides (OPs) exposure may be associated with increased risk of immunotoxicity in occupationally work place. The study was designed to investigate and compare the correlation between clinical symptoms with oxidative stress and immunomodulatory effects of OPs exposure among occupationally exposed researchers. Clinical manifestation associated with pesticides exposure were collected from 49 subjects occupationally exposed to OPs (exposed group), and 51 non-exposed subjects (control group). The levels of cholinesterase enzymes (AchE and BuChE) have been estimated as an exposure biomarker for pesticides exposure. The oxidative stress status has been evaluated by assessment of malondialdehyde (MDA), while total antioxidant capacity (TAC) could be an indication of antioxidant mechanism. We used IL-6 and IFN-γ as immunological biomarkers as well as TNF-α as a biomarker of cellular immune function. Our results revealed significant decline in AchE, BuChE and TAC level, while there was a significant elevation in MDA in occupationally exposed researchers versus control. Additionally, the IL-6, IFN -γ and TNF-α levels have been increased in exposed researchers. Through clinical examination, the chief morbidity was pertained to neurological disorders and bronchial asthma as a result of occupational exposure to OPs pesticides. The muscular weakness was significantly syndicated with the decline in AchE and BuChE levels. The bronchial asthma was highly correlated with MDA, IL 6 and TNF-α. Additionally, MDA, IL-6, IFN-γ, TNF-α, were significantly higher in numbness. This study also indicated that the levels of MDA, IL-6, TNF-α were significantly boosted up in exposed researchers that not wearing a mask. That could be a risk factor for some adverse health hazards.